A case of atypical Spitz tumor mimicking malignant melanoma

Abstract

A 9－year－old boy had a 10×7－mm² dark－brownish nodule on his right lower leg. The result of a partial biopsy performed at another hospital revealed the presence of a Spitz nevus. After the biopsy, the nodule extended by 4 mm in half a year ; thereafter, he was referred to our hospital. We performed a complete resection with a 5－mm margin. In our hospital, the first pathological diagnosis was malignant melanoma. Thereafter, we consulted dermatopathologists, and the nodule was finally diagnosed as an atypical Spitz tumor. The result of a sentinel lymph node biopsy was negative. No evidence of recurrence or metastasis was detected within 33 months postoperatively. The diagnosis of an atypical Spitz tumor requires immunohistochemistry and molecular studies as well as the evaluation of histological features. The identification methods for an atypical Spitz tumor, including sentinel lymph node biopsy, are challenging and controversial.[Skin Cancer (Japan) 2020 ; 35 : 65－70]